PCB in plant discharge. The EPA sets a limit of 5 parts per million (ppm) on PCB (polychlorinated biphenyl, a dangerous substance) in water. A major manufacturing firm producing PCB for electrical insulation discharges small amounts from the plant. The company management, attempting to control the PCB in its discharge, has given instructions to halt production if the mean amount of PCB in the effluent exceeds 4 ppm. A random sample of 50 water specimens produced the following statistics: x = 4.1 ppm and s = .5 ppm.

a. Do these statistics provide sufficient evidence to halt the production process? Use a = .01.

b. If you were the plant manager, would you want to use a large or a small value for a for the test in part a?